2 regular expression code snippets a developer needs daily

Regular expression can be easily called the heart of data mining technology. For beginners it may look like a very hard thing to grasp, But actually it’s pretty simple and compact once it’s been learned.

I have listed some pretty basic regular expressions here , Which can help in mining nearly 70% of the text available on the web.

1) Validate username, consist of alpha-numeric (a-z, A-Z, 0-9), underscores, and has minimum 5 character and maximum 20 character. You could change the minimum character and maximum character to any number you like.

2) Need to highlight repeating words in the text, This regex can become very handy.

$text = "This is a sample test written by Gaurav Mishra This is a sample test written by Gaurav Mishra This is a sample test written by Gaurav Mishra This is a sample test written by Gaurav Mishra This is a sample test written by Gaurav Mishra";
$text = preg_replace("/b(Gaurav)b/i", '<span style="background:#5fc9f6">1</span>', $text);
echo $text;